When middle school student Jun Tendou is chased by a strange creature into a temple, he is shocked when the head priest, Genun, offers more details about the oni demon he had just evaded. Before he has time to consider this new information, Genun suddenly transports them both back in time to the Heian period, where Heian-kyo—the ancient city which would eventually become modern Kyoto—is facing regular attacks by these same oni. The nobles of Heian-kyo see Jun as their savior; as the descendant